The present invention relates to a mobile communication system which sets an asymmetrical data communication channel in which a transmission rate of communication data transmitted from a mobile station to a base station differs from a transmission rate of communication data transmitted from a base station to a mobile station.
FIG. 1 is a configuration view illustrating a conventional mobile communication system of Japanese Patent Application Laid-Open Hei 8-331153. In FIG. 1, reference numerals 1, 2, 3 and 4 designate a mobile station installed in a movable car and so on, low speed transmission means for transmitting communication data of a low transmission rate to a base station 5, high speed reception means for receiving communication data of a high transmission rate from the base station 5, and an up-link of a data communication channel, respectively. Reference numerals 5, 6, 7 and 8 designate the base station which radio communicates with the mobile station 1 belonging to a radio covered area, low speed reception means for receiving communication data of a low transmission rate from a mobile station 1, high speed transmission means for transmitting communication data of a high transmission rate, and a down-link of the data communication line.
An operation of this mobile communication system will be described below.
For example, when the mobile station 1 need transmit communication data to a communication apparatus (not shown) connected to a public communication network, the mobile station 1 receives a control channel of the base station 5 and transmits a call through the control channel allocated to the mobile station 1.
That is, the mobile station 1 transmits control information necessary for radio communication to the base station 5 through the control channel (for example, information to the effect that the mobile station 1 transmits communication data to the base station 5 at a low transmission rate, while the mobile station 1 receives communication data from the base station 5 at a high transmission rate).
When the control information is transmitted from the mobile station 1, the base station 5 transfers the control information transmitted from the mobile station 1 to a mobile switching center and so on (not shown). After the mobile switching center and so on allow a request of the mobile station 1, the base station 5 sends information to the effect that the request has been allowed to the mobile station 1 through the control channel.
Thus, the transmission rate of communication data transmitted from the mobile station 1 to the base station 5 is set to a low transmission rate, while the transmission rate of communication data transmitted from the base station 5 to the mobile station 1 is set to a high transmission rate. Therefore, asymmetrical radio communication can be achieved in which the up-link 4 differs from the down-link 8 in the transmission rate.
Since the conventional mobile communication system is formed as described above, the asymmetrical radio communication may be achieved in which the up-link 4 differs from the down-link 18 in the transmission rate. However, means for changing the transmission rate of communication data is not provided. Thus, once the transmission rate of communication data is set, even though a data amount is changed in accordance with passed time, the transmission rate cannot be changed to a transmission rate corresponding to the changed data amount. The conventional mobile communication system has the above-described problem.
The present invention has been made to solve such a problem. It is an object of the present invention to provide a mobile communication system in which after the transmission rate of communication data is set once, the transmission rate of communication data may be changed appropriately.
In a mobile communication system of the present invention, a mobile switching center changes a transmission rate of communication data transmitted from a mobile station to a communication apparatus in accordance with a request from the communication apparatus and so forth connected to the mobile station, a public communication network or the like.
In such way, even though a data amount of communication data transmitted from the mobile station to the communication apparatus varies after the transmission rate of communication data has been set once, the transmission rate may be appropriately changed to a transmission rate corresponding to the changed data amount.
In the mobile communication system of the invention, the mobile switching center changes a transmission rate of communication data transmitted from the communication apparatus to the mobile station in accordance with a request from the mobile station or the communication apparatus.
In such way, even though a data amount of communication data transmitted from the communication apparatus to the mobile station is fluctuated after the transmission rate of communication data has been set once, the transmission rate may be appropriately changed to a transmission rate corresponding to the changed data amount.
In the mobile communication system of the invention, the mobile switching center changes the transmission rate of communication data transmitted from the mobile station to the communication apparatus or communication data transmitted from the communication apparatus to the mobile station individually and independently in accordance with a request from the mobile station or the communication apparatus.
Thus, even though a data amount of communication data transmitted from the mobile station to the communication apparatus or from the communication apparatus to the mobile station is fluctuated after the transmission rate of communication data has been set once, the transmission rate may be appropriately changed to a transmission rate corresponding to the changed data amount.
In a mobile communication system of the invention, the transmission rate changed by the mobile switching center belongs to a range of high speed data transmission.
Thus, when the data amount is markedly large, the transmission time may be shortened.
In a mobile communication system of the invention, the transmission rate of communication data changed by the mobile switching center belongs to a range of medium speed data transmission.
Thus, radio communication corresponding to a data amount may be achieved.
In a mobile communication system of the invention, the transmission rate of communication data changed by the mobile switching center belongs to a range of low speed data transmission.
Thus, when a data amount is small, radio communication corresponding to the data amount may be achieved.
In a mobile communication system of the invention, the range of the low speed data transmission includes intermittent data transmission.
Thus, a data communication channel may be released in a period in which no communication data are transmitted.
In a mobile communication system of the invention, TDMA/TDD system, TDMA/FDD system, time-divided CDMA/TDD system, time-divided CDMA/FDD system or CDMA/TDD system is used as a transmission system of the high speed data transmission.
Thus, the high speed data transmission may be performed using the above system and so on.
In a mobile communication system of the invention, TDMA/TDD system, TDMA/FDD system, time-divided CDMA/TDD system, time-divided CDMA/FDD system or CDMA/TDD system is used as the medium speed data transmission.
Thus, the medium speed data transmission may be performed using the above system and so on.
In a mobile communication system of the invention, TDMA/TDD system, TDMA/FDD system, time-divided CDMA/TDD system, time-divided CDMA/FDD system or CDMA/TDD system is used as a transmission system of the low speed data transmission.
Thus, the low speed data transmission may be performed using the above system and so on.
In a mobile communication system of the invention, when there are a plurality of mobile stations which transmit/receive communication data through the base station, the mobile switching center is provided with a transition state control processor for managing a transition state of a transmission rate for each of the plurality of mobile stations.
Thus, even though there are the plurality of mobile stations which transmit/receive communication data through the base station, the transmission rate of communication data may be accurately changed.
In a mobile communication system of the invention, the mobile switching center is provided with a priority control processor for managing a setting operation of a data communication channel by the mobile switching center and a changing operation of a transmission rate by the mobile switching center.
Thus, the setting operation and so on of the data communication channel may be surely managed.
In a mobile communication system of the invention, when the mobile station registers a location thereof, the mobile switching center registers the kinds of the transmission rates to be handled by the mobile station and a rate switching time of the mobile station.
Thus, the mobile switching center may change the transmission rate of communication data promptly if necessary.
In a mobile communication system of the invention, the mobile switching center stores the transmission rate to be handled by the mobile station, and is provided with an information memory for storing the rate switching time of the mobile station.
Thus, the mobile switching center may surely grasp the transmission rate and so on to be handled by the mobile station.
In a mobile communication system of the invention, when the mobile station and the communication apparatus start transmission of communication data, the mobile switching center selects the maximum transmission rate allowable by a data communication channel in current use from among transmission rates to be handled by the mobile station and sends transmission rate information on the maximum transmission rate to the base station and the mobile station.
Thus, the transmission time of communication data may be shortened.
In a mobile communication system of the invention, the mobile switching center has sent the information of the transmission rate to the base station and the mobile station, and after the rate switching time of the mobile station stored in the information memory has passed, the mobile switching center sends switching timing information for ordering switching of the transmission rate to the base station and the mobile station.
Thus, the transmission rate may be changed promptly and surely.
In a mobile communication system of the invention, after having received the switching timing information from the mobile switching center, the base station and the mobile station start transmission/reception of communication data at a new transmission rate from a time slot included in a first frame after the base station and the mobile station receive the information.
Thus, the transmission rate may be changed promptly and surely.
In a mobile communication system of the invention, when it is detected that a movement speed of the mobile station exceeds a range of a pedestrian""s walking speed in the case that the movement speed is laid in the range of the pedestrian""s walking speed, the mobile station sends car""s movement speed information to this effect to the mobile switching center through the base station.
Thus, the time slot may be changed so that the time slot is suited to the car""s movement speed.
A mobile communication system of the invention, when the mobile station detects that the movement speed of the mobile station falls below a range of the car""s movement speed in the case that the movement speed is laid in the range of the car""s movement speed, the mobile station sends car""s movement speed releasing information to this effect to the mobile switching center through the base station.
Thus, the time slot may be changed so that the time slot is suited to the pedestrian""s walking speed.
In a mobile communication system of the invention, the mobile switching center is provided with an information memory for storing the car""s movement speed information in the case that the car""s movement speed information is sent to the mobile switching center from the mobile station through the base station.
Thus, the mobile switching center may surely grasp the fact to the effect that the movement speed of the mobile station is laid in the range of the car""s movement speed.
In a mobile communication system of the invention, the mobile switching center is provided with an information memory for storing the car""s movement speed releasing information in the case that the car""s movement speed releasing information is sent to the mobile switching center from the mobile station through the base station.
Thus, the mobile switching center may surely grasp the fact to the effect that the movement speed of the mobile station is laid in the range of the pedestrian""s walking speed.
In a mobile communication system of the invention, the mobile switching center is provided with a system setting processor for changing a time slot so that a guard time of a data communication channel is suited to the car""s movement speed in the case that the car""s movement speed information is stored in the information memory.
Thus, the guard time of the data communication channel may be held to an appropriate value.
In a mobile communication system of the invention, the mobile switching center is provided with a system setting processor for changing a time slot so that a guard time of a data communication channel is suited to the pedestrian""s walking speed in the case that the car""s movement speed releasing information is stored in the information memory.
Thus, the guard time of the data communication channel may be held to an appropriate value.
In a mobile communication system of the invention, when the communication data are transmitted from the communication apparatus to the mobile station, the communication apparatus sends a data amount of the communication data to the mobile switching center.
Thus, the mobile switching center may grasp the data amount of the communication data. Therefore, when the communication apparatus transmits a large amount of communication data, the mobile switching center may judge if the mobile station may surely receive the large amount of the communication data or not.
In a mobile communication system of the invention, when the communication data are transmitted from the mobile station to the communication apparatus, the mobile station sends a data amount of the communication data to the mobile switching center.
Thus, the mobile switching center may grasp the data amount of the communication data. Therefore, when the mobile station transmits a large amount of communication data, the mobile switching center may judge if the communication apparatus may surely receive the large amount of the communication data or not.
In a mobile communication system of the invention, when the communication data are transmitted from the communication apparatus or the mobile station to another communication apparatus or another mobile station, the communication apparatus or the mobile station which transmits the communication data sends a data amount of the communication data to the mobile switching center.
Thus, the mobile switching center may grasp the data amount of the communication data. Therefore, when the communication apparatus or the mobile station transmits a large amount of communication data, the mobile switching center may judge if another communication apparatus or another mobile station may surely receive the large amount of the communication data or not.
In a mobile communication system of the invention, the mobile switching center determines the practicable maximum transmission rate on a basis of the maximum transmission rate to be executed by the mobile station and a state of currently empty data communication channels, judges if the data amount sent from the communication apparatus is transmittable within a predetermined time or not when the communication apparatus starts transmitting the communication data at the maximum transmission rate, and when judging that the data amount is not transmittable within the predetermined time, the mobile switching center disallows the transmission of the communication data.
Thus, reception errors of the communication data may be prevented.
In a mobile communication system of the invention, the mobile switching center determines the practicable maximum transmission rate on a basis of the maximum transmission rate to be handled by the mobile station and a state of currently free data communication channels, judges if the data amount sent from the mobile station is transmittable within a predetermined time or not when the mobile station starts transmitting the communication data at the maximum transmission rate, and upon judging that the data amount is not transmittable within the predetermined time, the mobile switching center disallows the transmission of the communication data.
Thus, reception errors of the communication data may be prevented.
In a mobile communication system of the invention, the mobile switching center determines the practicable maximum transmission rate on a basis of the maximum transmission rate to be handled by the mobile station and a state of currently free data communication channels, judges if the data amount sent from the communication apparatus or the mobile station transmitting communication data is transmittable within a predetermined time or not when the communication apparatus or the mobile station starts transmitting the communication data at the maximum transmission rate, and upon judging that the data amount is not transmittable within the predetermined time, the mobile switching center disallows the transmission of the communication data.
Thus, reception errors of the communication data may be prevented.
In a mobile communication system of the invention, when hand-over of the mobile station is carried out, the mobile switching center changes the transmission rate between the mobile station and a switched base station in accordance with a free data communication channel state of the switched base station.
Thus, the transmission rate of communication data may be optimized each time the hand-over of the mobile station is performed.
In a mobile communication system of the invention, the mobile switching center determines the switched base station before the hand-over of the mobile station is carried out, and judges the free data communication channel state of the switched base station.
Thus, disconnection of radio-connection caused due to the hand-over of the mobile station may be prevented.
In a mobile communication system of the invention, the mobile station detects electric field strength of radio waves transmitted from all the base stations adjacent to the base station to which the mobile station is connected at present to send the electric field strength to the mobile switching center.
Thus, the standard for selecting the optimal base station may be offered to the mobile switching center.
In a mobile communication system of the invention, when receiving an instruction from the mobile switching center, the mobile station sends the electric field strength to the mobile switching center.
Thus, the mobile switching center may obtain the electric field strength if necessary.
In a mobile communication system of the invention, in case of receiving an instruction from the base station, the mobile station sends the electric field strength to the mobile switching center.
Thus, when the base station judges that the mobile switching center requires the electric field strength, the mobile switching center may obtain the electric field strength if necessary.
In a mobile communication system of the invention, the mobile switching center compares the electric field strength of radio waves transmitted from the respective base stations with one another, and determines that a base station which transmitted a radio wave having the maximum electric field strength is made to be the switched base station.
Thus, the mobile switching center may determine the optimal base station as the switched base station.
In a mobile communication system of the invention, the mobile switching center selects a data communication channel which may achieve the maximum transmission rate in a range of the maximum transmission rates to be handled by the mobile station from among free data communication channels of the switched base station.
Thus, the transmission rate of communication data may be optimized each time the hand-over of the mobile station is performed.
In a mobile communication system of the invention, when the transmission rate is increased by carrying out the hand-over of the mobile station, the mobile switching center performs the hand-over before changing the transmission rate.
Thus, the hand-over of the mobile station may be performed promptly.
In a mobile communication system of the invention, when the transmission rate is decreased by carrying out the hand-over of the mobile station, the mobile switching center performs the hand-over after changing the transmission rate.
Thus, disconnection of radio-connection caused due to the hand-over of the mobile station may be prevented.
In a mobile communication system of the invention, when the transmission rate of communication data transmitted from the mobile station to the communication apparatus is increased, the mobile switching center checks for transmission power of the mobile station before increasing the transmission rate.
Thus, the mobile switching center may judge if the transmission rate of communication data may be actually increased or not.
In a mobile communication system of the invention, when the transmission rate of communication data transmitted from the communication apparatus to the mobile station is increased, the mobile switching center checks for transmission power of the base station before such an operation.
Thus, the mobile switching center may judge if the transmission rate of communication data may be actually increased or not.
In a mobile communication system of the invention, the mobile switching center checks for the transmission power of the mobile station by checking for received power of the base station.
Thus, the mobile switching center may surely confirm the transmission power of the mobile station.
In a mobile communication system of the invention, the mobile switching center checks for the transmission power of the base station by checking for the received power of the mobile station.
Thus, the mobile switching center may surely confirm the transmission power of the base station.
In a mobile communication system of the invention, the mobile switching center sends an instruction to enhance a transmission power level to the mobile station, and sends an instruction to send the received power to the base station.
Thus, the mobile switching center may judge if the transmission rate of communication data may be actually increased or not.
In a mobile communication system of the invention, the mobile switching center sends an instruction to enhance a transmission power level to the base station, and sends an instruction to send the received power to the mobile station.
Thus, the mobile switching center may judge if the transmission rate of communication data may be actually increased or not.
In a mobile communication system of the invention, when an increase in the transmission power of the mobile station corresponding to the change in the transmission rate is not obtainable, the mobile switching center disallows the change in the transmission rate.
Thus, when the transmission rate cannot be increased, the occurrence of a useless process of increasing the transmission rate can be prevented, and at the same time the occurrence of a communication abnormality resulting from such a process can be prevented.
In a mobile communication system of the invention, when an increase in the transmission power of the base station corresponding to the change in the transmission rate is not obtainable, the mobile switching center disallows the change in the transmission rate.
Thus, when the transmission rate cannot be increased, the useless process of increasing the transmission rate can be prevented from being caused, and at the same time communication abnormality resulting from such process can be prevented from being caused.
In a mobile communication system of the invention, when an increase in the transmission power of the mobile station corresponding to the change in the transmission rate is obtainable, the mobile switching center allows the change in the transmission rate.
Thus, the transmission rate of communication data can be increased.
In a mobile communication system of the invention, when an increase in the transmission power of the base station corresponding to the change in the transmission rate is obtainable, the mobile switching center allows the change in the transmission rate.
Thus, the transmission rate of communication data can be increased.
In a mobile communication system of the invention, when the transmission rate is doubled, the mobile switching center sends an instruction to enhance the transmission power by 3 dB to the mobile station.
Thus, the transmission rate can be doubled.
In a mobile communication system of the invention, when the transmission rate is doubled, the mobile switching center sends an instruction to enhance the transmission power by 3 dB to the base station.
Thus, the transmission rate can be doubled.